Mechanisms of Edema Formation in Myxedema — Increased Protein Extravasation and Relatively Slow Lymphatic Drainage

Abstract

We assessed extravascular accumulation of albumin and fluid in primary myxedema by measuring metabolic turnover and transcapillary escape of ¹³¹I-labeled human albumin in seven patients. In the hypothyroid state, we found a low plasma volume (P<0.05), a reduced rate of albumin synthesis and catabolism (P<0.01), an increased transcapillary escape rate of albumin (P<0.01), a remarkable increase in the extravascular mass of albumin (1500 μmol; P<0.01) and a longer mean transit time through the extravascular spaces in primary myxedema than in other states of generalized edema (P<0.05). All variables returned to normal during /-thyroxine treatment.